A request for a high speed of a signal processed in an electronic circuit and a miniaturization of a device is outstandingly increased. Thus, in the field of a connector, various proposals are presented to meet a high speed and high density signal circuit. One of important things for the connector is a matching of impedance to meet the high speed of the signal. In the matching of impedance (an impedance matching), when the impedances of signal circuits which are connected to each other are mismatched with each other, since a reflection of the signal arises in a connecting part (a connector part) of the signal circuits respectively, the impedance is matched with a prescribed impedance (for instance, 75Ω, 95Ω, etc.). It is important to suppress the occurrence of a reflected wave of a high frequency signal by taking the matching of impedance for achieving an acceleration of a signal transmission speed.
Therefore, usually, a method for obtaining a matching of impedance by adjusting an area of a main body part of a terminal is disclosed in, for instance, patent literature 1. This method is unique as a method for obtaining the matching of impedance. However, when an optimum form is designed, since an adjustment is required by changing a metal mold, this method is not suitable for a small quantity of production.
Further, a method for adjusting an impedance so as to be reduced by adjusting an opposed area to an adjacent contact is disclosed in patent literature 2. This method cannot meet an impedance lower than a prescribed impedance in view of design.
Further, patent literature 3 discloses a connector having an insulator and two or more connector parts arranged in parallel in the insulator in which the insulator is formed with a resin component obtained by mixing 5 to 85 wt % of ceramics dielectric powder having 30 or more of relative dielectric constant measured under 1 MHz at 25° C. in a matrix resin. According to this method, impedance can be changed without changing a form of the connector. In this method, since the impedance is determined in accordance with the relative dielectric constant of a resin material to be used, an inconvenience arises that flexibility in design of the connector is not obtained.
Thus, in a connector for a coaxial cable having a structure that supports an inner terminal for connecting a core wire through an insulating member, an area arises in which a shield is insufficient, so that impedance is high in the vicinity of the area to generate the reflected wave as described above or cause a transmission efficiency to be deteriorated in that part. In this case, the form (the thickness) of the insulating member is adjusted to adjust the relative dielectric constant of a resin material so that the impedance may be adjusted. However, in this case, an operation is necessary for pressing-in the inner terminal to an accommodating hole of the insulating member having a prescribed relative dielectric constant. When the insulating member is formed to be thin in order to lower the impedance, an inconvenience is caused to occur that an insulating coat is damaged or the inner terminal is broken during the pressing-in operation.
On the other hand, in order to avoid the inner terminal from being broken, a method is contemplated to apply an insert molding to the inner terminal by a resin material by using a metal mold. In the insert molding, a pressing-in operation of the inner terminal to the insulating member is not necessary. Thus, the damage of the insulating coat or the injury of the inner terminal can be avoided. Further, although the insulating member is formed to be thin so as to obtain prescribed impedance, the inner terminal can be assuredly integrally held.